The Hitchhiker’s Guide to Serial Communications

It is a well-known phenomenon that the inhabitants of Planet Earth love to create technological gaps between what has just been invented (and can be readily purchased), and what kind of equipment is actually installed in their hospitals, factories and other industries. Like the rules of their game of cricket and their lingering love affair with polka music, this is something humans have never been able to explain to fellow sentient creatures. It has, in fact, called into question their right to be regarded as fellow sentients at all.

Many humans have huge investments in legacy serial equipment. So the natural human response was to invent an entirely different universal bus called USB, and to equip new computers for USB while eliminating the serial port. (Never mind the fact that the serial protocol is still so useful to their species that the number of deployed serial devices is expected to keep growing for years to come.) Fortunately, in spite of everything the humans have tried to do to prevent it, it’s actually quite easy to get their serial devices to talk to their networks. You can even get their serial devices to talk to their smart phones and tablets. Grab your towel and your notepad, and we’ll tell you all about it.

Here, in the form of a video, is a fun, but educational look at serial
communications and the transition to USB and Ethernet. Serial devices
can now communicate anywhere and everywhere. Solutions target the industrial
communication technology gap.

The human objection to serial communications

Serial communications based on RS-422 and RS-485 communicates digital information over twisted pair wire from transmitters to receivers. RS-422/485 systems can communicate at rates up to 10 Mbps (though most systems operate at lower bit rates). Both systems utilize balanced outputs and differential inputs, which provide better noise immunity than single-ended systems. RS-485 is used as the basis for many commercial and industrial data communications systems, like Profibus, Interbus and Modbus.

Serial communications are commonly used to link programmable logic controllers (PLC), supervisory control and data acquisition (SCADA) systems, remote terminal units (RTU) and other equipment in custom networked systems. The RS-422 and RS-485 standards do not define protocols. They are simply physical layer standards (and even then, do not specify connectors or pin-outs). This means that RS-422 and RS-485 can be implemented in many systems and applications. This was all working very well, which is why humans invented USB to replace it.

USB uses completely different protocols, completely different cabling and completely different ports. Better still, it has an effective range of only 15 meters. Granted, that can be extended up to 30 meters using USB hubs like B&B Electronics’ UHR204. But it’s still just a fraction of the 4000 ft. range achieved by RS-485, which -- to humans – was a key selling point. Additionally, USB connectors don’t grip the cables very firmly, unless you’re using high retention ports like those, for example, in B&B Electronics’ USOPTL4. As USB carries 5 V DC power, this creates an opportunity for fire when vibration shakes a cable loose. Humans love fires, and they report them on the news whenever they think they’ve had a good one. Serial connectors generally employ thumbscrews to hold them in place. This reduced ability to create newsworthy conflagrations was one reason for trying to move away from the serial standard.

Serial Communications and the Expansion Port

Humans equip their desktop computers with card slots that allow computers to be configured in numerous ways and for numerous purposes. As new generations of computers are designed and built, the nature of this bus is continually reconfigured in order to keep older cards from functioning in newer machines. Humans love to recycle, and they are enchanted by the fact that an ISA card that once sold for $175 can be broken down into its constituent elements and recycled for a total profit of three cents.

The more often the humans change their standard computer bus, the more expansion cards will -- some day, even if it’s in the distant future -- become available for recycling. When a computer is not equipped with serial ports humans are quite happy to install them using serial port expansion cards like B&B Electronics’ 3PCIUx series. It would seem that this flies in the face of the usual human desire to avoid having data communications be easy and turnkey. A machine that was not built for serial data communications can suddenly do it. But humans love to consider the fact that – if they just hang in there and wait long enough – they will eventually get to recycle nearly everything they own.

This is the basis of what humans call “consumerism,” and it’s one reason that they don’t object to adding serial port functionality to their computing equipment.

Serial to Ethernet

Humans invented the TCP/IP protocol as a step toward the creation of social media networking sites, which – in combination with texting -- humans use to keep one another informed about everything they do, think, see, hear, eat, smell or happen to be standing next to. It has been a genuine revolution in human affairs, as humans can now keep thousands of fellow humans, all around the planet, completely informed, at all times, about what they’re considering having for lunch.

If a human tried a new beverage for the first time, he or she could inform the world, at a moment’s notice, that the beverage was, “almost, but not quite, entirely unlike tea.” It’s mind-boggling. But the TCP/IP protocol has turned out to have some less important applications as well. The human business community, for example, has discovered that TCP/IP can be used for purposes that have nothing whatsoever to do with eating lunch.

Ethernet now appears in everything from smart power grids to facility management, and it brings humans great joy to consider the fact that their great-grandchildren, or perhaps their great, great-grandchildren, will eventually get to tear all of this stuff down and recycle it. It’s believed that the first attempt at building a serial-to-Ethernet server was made by a social networking-obsessed human scientist who realized that while he could share his lunch plans, mood rating and uninformed political opinions with millions of human beings all over the planet, things like serial-equipped industrial robots and gasoline pumps were being left completely out of the loop. It’s thought that he may have succeeded, as the industrial robot promptly unplugged itself and tried to escape. But both the scientist and his notes were lost when a loose USB cable caused a five-alarm fire that made it on to the AP wire and was picked up for news broadcasts in 27 states.

More advanced serial-to-Ethernet servers like B&B Electronics’ ESP211 have subsequently been developed. It’s unlikely that any serial-enabled device will ever actually care whether a human has discovered a new beverage that is almost, but not quite, entirely unlike tea. But serial devices will, at least, communicate with Ethernet networks.

Serial Communications with Tablets and Smart Phones

It was obvious that allowing smart phones and tablets to interact with serial devices would be incredibly useful to a great many people, so humans have done their best to keep this from happening. They’ve designed their smart phones and tablets to use Wi-Fi as the primary means of communication, thus isolating these devices from as much of their older equipment as possible. But they have also invented the embedded wireless access point.

The Quatech APMG-Q551, for example, creates a small, self-sustaining Wi-Fi network around remote equipment. Its purpose is to interfere with data communications by ensuring that the majority of the Wi-Fi devices on Planet Earth will always be completely out of range. This strategy has an inherent flaw, however. When a Wi-Fi device like a tablet or a smart phone is physically carried into the embedded Quatech APMG-Q551’s broadcast hotspot, there is no known way to prevent the tablet or phone from communicating successfully with the access point-equipped device. It is safe to assume that humans are working on this problem. But, for now, there is nothing to stop a technician from walking up to any access point-equipped device that he or she chooses, any time that he or she chooses, and successfully establishing a data communications link using a smart phone, tablet or laptop computer.

Don’t Panic!

If you’re currently doing business on Planet Earth you already know that their data communications standards are always in a constant state of flux. But don’t panic. There’s always a way to make human data communications devices interact. And as for the inhabitants themselves, they’re mostly harmless.

The article is much funnier than the video. At least for those of us that actually still read books on our iPads. A few of us even remember paper which we enjoyed recycling before we ever had a chance to read all the articles in EE Times. I enjoyed the creativity.

A curmudgeon after my own heart. They started taking the serial and parallel ports away with XP when they stopped letting you access them for bit banging without installing a driver. Now you need to install drivers and hardware to simulate a serial port on USB like the FTDI stuff. You see they needed to protect the computer from the user. The modern computer design philosophy is that it is not your computer. Microsoft, Oracle, Adobe and Google should be allowed unfettered access to your computer while you as the user should only be allowed the minimal access that they determine you need. WiFi and USB are major advances in monitoring, controlling and limiting the user's use of the computer.

Completely disagree with the criticism of USB. USB automates the negotiation of the data rate, error correction, and other settings that used to be done manually. And while using serial to Ethernet converters is convenient for legacy hardware -- the real fix is to place Ethernet interface directly on SCADA or PLC gear.
As an engineer who uses all of these technologies, I found nothing useful or insightful from the video. Granted it has some humor (about social networking). But that wasn't why Ethernet was invented.